7th fret capo and scales from this site.

I am trying to find a scale to use over a song I am writing. I have a capo on the 7th fret. How does this affect the position of scales on the guitar?

Since the chord fmaj7 becomes cmaj7 would I assume a normal C lydian scale would become F Lydian with the 7th fret capo?

Fmaj7 should still be Fmaj7. The only thing a capo affects is playing the strings open. For example playing the E string open would now produce a B instead of an E. Other than that, the notes don't change. It's like cutting off your guitar below that point. C lydian is still C lydian.

the notes are still the same. but, if you talking about some sort of relative transcription, you could just consider the open strings to be Eadgbe and adjust everything else accordingly, that's really probably not necessary though.